1. Technical Field
The present invention relates to a projection system for projecting a plurality of images in a condition in which positions of corresponding pixels of the images are identical to each other or shifted a predetermined amount from each other, an image processing device, and an image processing method in such a projection system.
2. Related Art
There is known a projection system for projecting a plurality of images in a condition in which positions of corresponding pixels of the images are identical to each other or shifted a predetermined amount from each other. In such a projection system, it is possible to achieve higher resolution of the image displayed on a projection surface by, for example, projecting images respectively from a plurality of projectors (two projectors are assumed here only for the sake of simplicity of explanations), while setting the positions of the corresponding pixels of the two projectors so as to be shifted ½ pixel in a oblique direction from each other. Further, it is possible to achieve higher resolution of the image displayed on the projection surface by projecting images respectively from a plurality of projectors (the two projectors are assumed in the same basis) while setting the positions of the corresponding pixels of the two projectors so as to be identical to each other.
In such projection systems, in either of the cases, it is important for the pixels of the two projectors, corresponding to each other to be kept in an accurately positioned state.
Considering, for example, a projection system (referred to as a first projection system) for performing projection while shifting pixels of two projectors, which correspond to each other, ½ pixel in an oblique direction, even if the positions of the corresponding pixels of the two projectors are accurately adjusted so as to be shifted ½ pixel in the oblique direction from each other when building up the first projection system, pixel shift might be caused in the ideal positions of pixels (referred to as ideal pixel positions) set initially in each of the projectors due to the variation with time. Such pixel shift to the ideal pixel positions also causes degradation in sharpness of the image displayed on a screen as the projection surface.
FIGS. 9A and 9B are diagrams for explaining the pixel shift to the ideal pixel positions. FIG. 9A shows the state in which the pixels corresponding to each other of the two projectors are set in the ideal pixel positions, and in this case, the pixels P11, P12, . . . (indicated by outline rectangles) of one projector PJ1 out of the two projectors PJ1, PJ2 and the pixels P21, P22, . . . (indicated by gray rectangles) of the other projector PJ2 are in the state in which the pixels (e.g., the pixel P11 and the pixel P21, or the pixel P12 and the pixel P22) corresponding to each other are shifted ½ pixel in an oblique direction from each other. It should be noted that in FIGS. 9A and 9B only an opening section of each pixel in a light modulation element (assumed to be a liquid crystal panel) is shown, but a black matrix section thereof is omitted. This is also applied to FIGS. 6A and 6B explained later.
Further, FIG. 9B shows the case in which the position of the light modulation element is displaced due to some cause in the state shown in FIG. 9A, and the shift (referred to as the pixel shift) with respect to the ideal pixel position (the pixel position shown in FIG. 9A) is caused in the position of each pixel of the light modulation element, and in this case, it is assumed that the pixel shift is caused in each of the pixels of the projector PJ2 based on the position of each of the pixels P11, P12, . . . of the projector PJ1.
Here, assuming that the positions of the pixels P21, P22, . . . of the projector PJ2 relative to the positions of the pixels P11, P12, . . . of the projector PJ1 in the ideal pixel positions are (ri, θi), and the positions of the pixels of the projector PJ2 relative to the positions of the pixels of the projector PJ1 when the shift of the pixels from the ideal pixel positions occur are (rf, θf), the pixel shift amount (r, θ) of the projector PJ2 with respect to the ideal pixel positions can be expressed as the following formula 1.(r,θ)=(rf−ri,θf−θi)  (1)Therefore, by correcting the pixel shift amount obtained by the formula 1, the positions of the corresponding pixels of the two projectors PJ1, PJ2 can be set to be the ideal pixel positions (see FIG. 9A). It should be noted that as a method of determining the pixel positions (ri, θi) and (rf, θf) of the respective pixels, a method, for example, of adopting a peak position of a luminance distribution of that pixel can be exemplified.
Further, also in the projection system (referred to as a second projection system) having the two projectors PJ1, PJ2 adjusted so that the pixels thereof corresponding to each other are positionally identical to each other, the pixel shift amount from the ideal pixel position can be obtained.
In the first projection system and the second projection system, if the pixel shift with respect to the ideal pixel position occurs, degradation in sharpness of the image displayed on the screen is caused, and therefore, some measures for correcting the degradation in sharpness of the image become necessary. As the measures for correcting the degradation in sharpness of the image, a pixel position correction section for correcting the pixel shift with respect to the ideal pixel positions is provided, and by correcting the pixel shift using the pixel position correction section, the degradation in sharpness of the image can be corrected.
As such a pixel position correction section, for example, a positioning mechanism of the light modulation element capable of fine-adjusting the position of the light modulation element can be exemplified, and a projector incorporating such a positioning mechanism has been known in the past (see, e.g., JP-A-2006-10993 (Document 1)).
The technology disclosed in the Document 1 is for enabling an actuator to fine-adjust the light modulation element, and by providing such a positioning mechanism of the light modulation element to each projector, it becomes possible to correct the pixel shift with respect to the ideal pixel positions.
For example, as shown in FIGS. 9A and 9B, when the pixel shift occurs with respect to the ideal pixel positions in the first projection system for performing projection while shifting the corresponding pixels of the two projectors ½ pixel in an oblique direction, it is possible to correct the positions of the corresponding pixels of the two projectors to be the ideal pixel positions by making the positioning mechanism of the light modulation element operate in one of the two projectors, and it is conceivable that the degradation in sharpness of the image due to the pixel shift with respect to the ideal pixel positions can thus be corrected.
However, since the technology disclosed in the Document 1 is for moving the light modulation element using a mechanical positioning mechanism, it is required to dispose the positioning mechanism with a complicated configuration inside the projector. Therefore, the internal configuration of the projector becomes complicated, and further, downsizing and weight saving of the projector are inhibited. Further, the higher the resolution of the light modulation element becomes, the more accurately the positioning needs to be executed, and the adjustment accuracy of, for example, several hundreds of nanometers might be required. Therefore, the adjustment using a mechanical positioning mechanism such as an actuator might substantially be difficult in some cases.